Yes, several times over the years. Usually I've gone back for it or stopped at a store to pick up something to drink; but, last week I noticed that I didn't have any water about a 1/4 mile from home and just kept going since it was about 40F and I was only planning on riding ~10 miles.

Yep.
Water, helmet, gloves, and sunglasses one time or another.
Give me more time, I'm sure I'm not done with my list yet.

I've forgotten everything at one time or another. Water...garmin gps...rain jacket...tire repair kit...mini pump....you name it, I've forgotten it. It's just a talent I have.

At least you remembered your clothes.....right?....

I've forgotten my water bottle so often that I have a map in my head of the coffee places in my area that have a water cooler and cups inside the door so I can grab a drink in an emergency. These are also the coffee places I do business with when I am on a ride and DON'T forget my water bottle. They're good to me, so I am good for them.

We live in the Sonoran Desert . . .
On long rides we carried 7 water bottles on the tandem; it can be 50 miles between watering opportunities and 100+ degrees 'warm'.

I'm not sure I've "forgotten" my water bottle, although I suppose I've forgotten to take the opportunity to refill mid-trip.

I blew out a rivnut on my Litespeed. I'll get it fixed.... soon. But, until then, it is either Camelback, or nothing. So, trips to town, I just go without.

Not my whole bike but my front wheel. Too bad to, I had my water.

I've never forgotten my water for a ride (yet). I've under-estimated how much I'd need, but never forgotten it.

But... several years ago I forgot my water on a summertime solo whitewater kayak ride on the Cheat River Narrows in West Virginia. Started out with the hike back up to where the boat was waiting beside the river - several miles in direct sun. And when I got there - I'd forgotten to put the water in the boat. Baaaad news.

I was really hurting by the time I got back to the car - weak & dizzy. I took a big drink of water - and immediately threw it right back up. Spent half an hour laying on the front seat in the air conditioning, taking small sips before I felt able to load the boat and drive. Scared the daylights out of myself that day, but I don't forget my water anymore.

Steve Z

In the good old days of athletic training, it used to be common to go without water intentionally, so as to get used to exercising while thirsty. To toughen up. Maybe even as a deterrent to perspiration.

I admire that spirit.

But when I'm riding I always take a water bottle, without fail.

My wife forgot her helmet once. She noticed it when we got to the bottom of a hill after taking a break at the top. So, back up we went. No helmet. We found it back in the car. My wife hates hills.

I often forget my water bottle at home. I don't worry about it because I have two bottles on my bike and usually use just one. I also keep two spares in the van. Also, the MUP I ride at has cold water stations every 1.5 miles. When I don't ride at the MUP and forget my filled water bottle, I'll stop at a drive through and ask them to fill my second bottle.

I usually do forget it It's gotten so habitual that I've given in to reality and I usually have a cut-down water bottle in one of my holders, a catch-all for sunglasses, gloves etc. Since I know I'll forget the water anyway.

I have forgotten my water bottle a number of times when leaving on my commute home from work, perhaps a few times in the morning as well. My commute distance is about 15-16 miles each way, so I can do it with no water but I drink up when I get home or to work. The only times it's been tough was on hot summer days. I normally drink a lot of water (see the thread on kidney stones) while riding, so I typically notice the missing bottle within a few miles but never turn back.

I ride Where water is served (too)

Not that I remember. Filling/checking my tires and water bottle are a pre-ride ritual.

I have loaded my bike after a ride, and driven off with my water bottle on the back bumper.

Often I'll drive straight from work to the lake for a club bikeride or to ride solo.
I pack the car with bike, clothes, shoes, all my bike stuff.
I take 2 waterbottles into my workplace to fill with ice/water on my way out.

I do keep a spare bottle at work, but one 24-oz bottle isn't enough for a hot summer ride.
On our club route, there isn't a place to refill bottles mid-ride with cold water.
Dehydration is a chronic issue with me.
Borrowing a bottle from a friend isn't an option either. They need both their bottles too.

No water = no ride. And insufficient water = no ride.

Not always! Drove several hours to a ride that was just part of a long day and one that I was doing on a new bike that had almost all of my attention. Got there and guess what? No jersey , no shoes. There was a surprisingly good bike shop in town and I purchased a perfect fitting pro racing quality jersey and some MTB shoes (I had toeclips; this was to be a fix gear ride with 2000' of climbing and descending - I don't do clipless there). Each was a C note. Ouch. But the ride went very well and even the shoes weren't an issue. And now,a few years later, I am riding SPD pedals and cleats on a gravel grinder/snow bike with MTB boots. Those shoes now have their place.

I have forgotten virtually everything at some point. Not yet the bike. I have forgotten my glasses. That's interesting. Locks (cost me a bike once), tires, tubes, tools.

Ben

One day I was going out for a short spin and ended up further out than originally planned. Problem was I forgot my water and it was hot day, (90's). I was parched and getting ready to turn around when I came across a road crew. I told them I forgot my water and they gave me some, (from the yellow igloo you always see on the back of their trucks. Well, it was enough to keep going until I reach a fast food joint where I quenched my thirst for the way home. Lucked out I guess.

I rode my bike to Eagle Alaska (loaded touring) then took the ferry to Dawson and rode home. Going West from Whitehorse I ran out of water. I had a filter but there was simply no lakes or streams and eventually I completely bonked. Sat on the side of the road pretty much unable to go further. I held up my empty bottle to beg water for quite some time. A woman passed me with hardly a glance and returned about 30min later with water. She had none but went and got some. How nice was that?

You weren't accused for failing to notice her helmetless head?

Does having a bottle full of water on the bike, but forgetting to drink count? If so, I've ridden 50+ and up to 100 miles without drinking countless times.

Not that time.

How long you been married?

My first anniversary is still a month or so away, but I've found that by chewing gum I don't get as thirsty and don't even think about water until that 15th mile.

It's a different story when it's hot, then I make a conscious effort to drink every 4-5 miles whether I need to or not.

But YES, I have forgotten water several times. If it's hot, I turn back, even if I'm 5 miles away. This is the over 50 section, right?

I've never forgotten the water bottle, but I have had the unpleasant experience of developing a kidney stone due to not getting enough water one summer while doing a lot of running. The subsequent lithotripsy experience was enough to make sure I always have water.