Can I get sponsored by just sending a DM or sponsorship deck to a brand?

No. Both Optima and Boxo representatives explicitly stated that sponsorships never come from DMs or unsolicited decks alone. Cam from Optima said he has 'never sponsored somebody via an agent that sent me a deck or that they personally sent me a deck or that they found my phone number and they called me out of the blue.' Every successful sponsorship relationship has come from either a trusted referral or knowing the person personally beforehand. A DM might start a conversation, but it will need to progress to emails and phone calls, and ultimately an in-person relationship.