For user acquisition hacks for a SaaS prototype, focus on leveraging targeted marketing channels such as social media advertising, content marketing, and email campaigns to reach potential users. Offer early access or beta testing opportunities to generate buzz and attract early adopters. Utilize referral programs, partnerships, and influencer collaborations to expand your reach and acquire users at a rapid pace. Additionally, engage in community building and networking within relevant online forums, groups, and events to establish credibility and attract interested users to your SaaS prototype.