Birdies Cofounders Bianca Gates and Marisa Sharkey Share Their Must Haves

"The most affordable must have is just hydrating drinking water; your makeup goes on better, your skin looks better, you feel better, you rest better, you perform better, you have more energy," Gates says, noting it doesn't cost much to refill a trusted water bottle like the Birdies Water Bottle ($22). She loves this one because it fits into the cup holder in her car. Gates drinks around 30 cups of warm water daily, and she raves about how this insulated water bottle can keep liquids hot, or cold, for a long time.

Pro Tip: Gates prefers to drink hot water because "it's so soothing. It calms your nerves, too, if you're ever nervous about something. And just holding it and just the hot steaminess of it when you're cold," she says, adding that it can help cool you down on a hot day as well.