There are a total of 5 Bottles to find in the game.
#1. In Level 1, after the Hippogriff fight but before Arma, you will reach a cliff with a moving platform near it. Drop down into the "pit" and you'll find the first bottle in an alcove.
#2. When you get the Water Crest, return to Level 2 and proceed to the water area. Use the Tidal Gargoyle to dive into the water. A bottle is hidden at the bottom of the lake beneath the arch.
#3. In the first area of the forest level, you will see a bottle out in plain view. However, it's protected by thorns. You can get it without taking damage if you have the Aerial Gargoyle or the Claw weapon, but if you don't mind taking a sacrifice hit, you can still get it without either of those items. Just be sure to have enough life power before attempting it.
#4. When you start ascending the tower in Level 4, you'll eventually notice a wall with a bunch of breakable bricks. Use the Buster weapon to cut through them, then walk through the wall. The bottle is in a small enclosed area at the end.
#5. As soon as you begin Level 6, fly straight up as the Aerial Gargoyle. You'll find a floating platform near the very top of the screen with the final bottle.