In every state it operates, DraftKings's sign-up offer is: Bet $5, get $150 in bonus bets paid over 14 days. Promonyx estimates it is worth $105, and it needs about $130 available at once. DraftKings's own site shows no promo code for it: the offer applies when you sign up.
DraftKings's offer is checked in 27 states: Arkansas, Arizona, Colorado, Connecticut, Washington DC, Iowa, Illinois, Indiana, Kansas, Kentucky, Louisiana, Massachusetts, Maryland, Maine, Michigan, Missouri, North Carolina, New Jersey, New York, Ohio, Oregon, Pennsylvania, Tennessee, Virginia, Vermont, West Virginia, Wyoming.
You place one qualifying bet with your own money, and the book credits bonus bets whether that bet wins or loses. A bonus bet pays out only its winnings, never its stake, which is why a bonus bet is worth less than the same amount in cash.
About $105 on $130 of cash needed at once, a 81% return. That is an estimate of the offer before it is placed, based on the book's terms and prices at the time.