We Used to Drink on the School Trips

Imagine this, twenty five kids on the bus going on the school trip, and once in the while some of them would take a bottle of Vodka from their knapsack and drink, including me. Yes, we used to drink, but it wasn't a Vodka, it was a tea or some kind of juice. Back then we didn't really have good drinking plastic bottles to bring our drink in, so we used whatever we had at home. Since the Vodka bottle was the only bottle with the screw top, that was the most popular bottle taken on the trip, some of them still with a label on it. So this is how we used to drink on the school trips in the elementary school. The scary part was that they actually let us drink on the bus while bus was in motion. Luckily we didn't damage our teeth. So one day here is me, drinking my Vodka from the bottle, suddenly I stand up on the bus and yelled out to my friend beside me - did you see this, wow? And suddenly my teacher gave me a look that I had to bury myself in the bus chair, turning red, and trying to drink my Vodka, and of course to pretend that nothing happened. Can you guess what I saw? I will give you some clues: it was in Europe, it was a big tree, parked bike on the side of the road.