1) Once you kill all the tadpoles, if you roll towards Deku Toad he will jump up straight away rather than waiting for him.
2) If you C-Up while Deku Toad is in the air he will fall down immediately.
3) When Deku Toad falls down he will always face the center of the room
Without bombs, the fastest way to kill the deku toad is with two sets of 10 well-timed non-combo slashes.
We can have bombs in Lakebed Temple but we don't have the master sword so we can't finish Deku Toad off in 1 cycle. With 3 bombs its still possible to kill him without a real second cycle.
After he drops from the floor the first time, place a bomb next to the tip of his tongue (kinda precise) and slash the bomb. As soon as he opens his mouth, throw another bomb into it and drop a final one on the ground next to where his tongue tip was before.
The normal strat for the Deku Toad 2 cycle with bombs has you kill the tadpoles and wait for the toad to fall down. It is possible with precise timing, however, to throw a bomb into his mouth with the boomerang at the very start of the fight, skipping this process and going straight into the knocked down portion of the 2 cycle, saving around 15 seconds. To do this, make sure you have bombs and the boomerang equipped when entering the room. Skip the cutscene, and while the game is loading the fight, hold zl, right on the control stick, and whatever button the bombs are on. This should buffer targeting the toad, walking a little to the right, and pulling out the bomb on the first frame, respectively. Then a few frames after the game loads, tap the boomerang button while continuing to hold zl. Link should throw the boomerang and the bomb should go into Deku Toad's mouth. The window for the throw is a little tight (only around two frames), but thanks to input buffering, it's only one tight window and not several. NOTE: if you do this trick and kill the worms in poe skip room with bombs, you will want to grab extra bombs in Arbiters Grounds.
Since we don't have the Master Sword in TPHD before Lakebed we can't just finish him off quickly with just the sword.
Instead just use 4 Bombarrows to kill him off. Make sure to hit him with the first Bombarrow before he starts with his first cycle.
Shoot the Bombarrow as soon as you can see Deku Toads tongue to skip the first tadpole cycle.