We establish Diophantine inequalities for the fractional parts of generalized polynomials f , in particular for sequences ν(n) = ⌊n c ⌋ + n k with c > 1 a non-integral real number and k ∈ N, as well as for ν(p) where p runs through all prime numbers. This is related to classical work of Heilbronn and to recent results of Bergelson et al.considered the Diophantine inequality over smooth numbers to obtain an improvement. The proofs of these results are based on a sophisticated treatment of the occurring exponential sums. In a recent paper Lê and Spencer [29] proved the following Theorem 1.2 ([29, Theorem 3]). Let N ∈ N and h ∈ Z[X] be a polynomial with integer coefficients such that for every non-zero integer q there exists a solution n to the congruence h(n) ≡ 0 mod q. Then there is an exponent η > 0 depending only on the degree of h such that min 1≤n≤N ξh(n) ≪ h N −η for arbitrary ξ ∈ R.