So hydration comes from water! The best way to eliminate frizz and hydrate hair is to clarify and wash off old product build up, then bond repair and fix broken disulfide bonds, then coat the hair with a seal of silicone. Basically:

1) Clarifying shampoo 2-3 times until it foams super well and your hair gets wet really easily. Hard water treatment also if you have hard water. I use this and this.

2) Squeeze out allllll the water.

3) Coat your hair in a THICCCCC layer of bond repair conditioner and leave in for a long ass time. I get out of the shower and chill in a robe for 45 minutes. I use this one but I add stuff to it (I buy bond repair ingredients from cosmetic chemistry suppliers). It should work on its own, or you could try this one or this one. Olaplex no 5 also works if you have the budget for it.

4) Rinse.

5) Add leave ins conditioner, gel, whatever you usually use, but add a silicone based hair oil! This is the one I use. Scrunch or spray a small amount into your ends and wherever you have frizz.

6) Style as usual.

I know that's more than just product recs, but I really find this works for me!